Method of optical measuring the microrelief of an object using a modulation interference microscope. An input coherent monochromatic polarized light flux is split into an object light beam exposing the object and a reference beam. The light flux intensity is redistributed between the object and reference beams. Thereafter, polarization modulation is performed separately for the object beam and the reference beam. The polarized object beam is reflected onto the object plane to expose the object field. Amplitude modulation is performed by changing the intensity ratio between the object beam and the reference beam. A fraction of the light at a pixel caused by the object beam with respect to the total light falling on the pixel is determined.